Lasers are used in a variety of different areas for performing a variety of different functions, Lasers can be designed to produce a continuous emission or a pulsed emission. For pulsed emission systems, it has been found that optical fibers such as Erbium doped fibers represent a particularly preferred gain medium for generating short optical pulses. However, optical fibers are extremely fragile and thus require great care in handling and usage. In one respect, if the optical fiber is bent too sharply (i.e., if the optical fiber is bent so as to possess an excessively small radius of curvature), signal loss can occur if some of the transmitted light leaks out of the fiber at the bend. Further signal degradation can occur if the radius of curvature of the optical fiber is so small that micro cracks are introduced into the fiber. Thus, for a given fiber, there exists a critical radius which is defined as the minimum radius of curvature for the fiber that will avoid the aforementioned problems.
In lasers that employ optical fibers such as Erbium doped fibers, the optical fiber must be of sufficient length, for example on the order of 2-3 meters, to achieve proper operating effectiveness of the laser. There is, however, also a desire to make the optical fiber laser as compact as possible. This objective of producing a compact laser is oftentimes difficult to achieve while at the same time satisfying the requirements that the optical fiber possess sufficient length and that the optical fiber not be bent so sharply as to possess a radius of curvature less than the critical radius.
U.S. Pat. No. 5,530,787 discloses a particular construction for a curved fiber guide that is designed to receive and guide a fiber in such a way as to avoid bending the fiber too sharply. While this proposal may be acceptable from the standpoint of ensuring that the fiber is not excessively bent, it suffers from the disadvantage that it is not well suited for use in constructing a relatively compact laser.
In light of the foregoing, a need exists for an optical fiber laser unit which is relatively compact in size while at the same time providing an optical fiber of sufficient length to operate effectively.
A need also exists for an optical fiber laser unit which is relatively compact in size yet which does not require that the optical fiber be bent so sharply that its radius of curvature is less than the critical radius.
It would also be desirable to provide a compact optical fiber laser unit that includes both a laser oscillator which produces optical pulses and a laser amplifier that amplifies the optical pulses to produce an optical pulse output of desired power.